1# SPDX-License-Identifier: GPL-2.0-only 2config CC_VERSION_TEXT 3 string 4 default "$(CC_VERSION_TEXT)" 5 help 6 This is used in unclear ways: 7 8 - Re-run Kconfig when the compiler is updated 9 The 'default' property references the environment variable, 10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 11 When the compiler is updated, Kconfig will be invoked. 12 13 - Ensure full rebuild when the compiler is updated 14 include/linux/compiler-version.h contains this option in the comment 15 line so fixdep adds include/config/CC_VERSION_TEXT into the 16 auto-generated dependency. When the compiler is updated, syncconfig 17 will touch it and then every file will be rebuilt. 18 19config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41config AS_VERSION 42 int 43 # Use clang version if this is the integrated assembler 44 default CLANG_VERSION if AS_IS_LLVM 45 default $(as-version) 46 47config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63config RUST_IS_AVAILABLE 64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 65 help 66 This shows whether a suitable Rust toolchain is available (found). 67 68 Please see Documentation/rust/quick-start.rst for instructions on how 69 to satisfy the build requirements of Rust support. 70 71 In particular, the Makefile target 'rustavailable' is useful to check 72 why the Rust toolchain is not being detected. 73 74config CC_CAN_LINK 75 bool 76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 78 79config CC_CAN_LINK_STATIC 80 bool 81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 83 84# Fixed in GCC 14, 13.3, 12.4 and 11.5 85# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 86config GCC_ASM_GOTO_OUTPUT_BROKEN 87 bool 88 depends on CC_IS_GCC 89 default y if GCC_VERSION < 110500 90 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 91 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 92 93config CC_HAS_ASM_GOTO_OUTPUT 94 def_bool y 95 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN 96 depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 97 98config CC_HAS_ASM_GOTO_TIED_OUTPUT 99 depends on CC_HAS_ASM_GOTO_OUTPUT 100 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 101 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 102 103config TOOLS_SUPPORT_RELR 104 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 105 106config CC_HAS_ASM_INLINE 107 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 108 109config CC_HAS_NO_PROFILE_FN_ATTR 110 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 111 112config PAHOLE_VERSION 113 int 114 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 115 116config CONSTRUCTORS 117 bool 118 119config IRQ_WORK 120 def_bool y if SMP 121 122config BUILDTIME_TABLE_SORT 123 bool 124 125config THREAD_INFO_IN_TASK 126 bool 127 help 128 Select this to move thread_info off the stack into task_struct. To 129 make this work, an arch will need to remove all thread_info fields 130 except flags and fix any runtime bugs. 131 132 One subtle change that will be needed is to use try_get_task_stack() 133 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 134 135menu "General setup" 136 137config BROKEN 138 bool 139 140config BROKEN_ON_SMP 141 bool 142 depends on BROKEN || !SMP 143 default y 144 145config INIT_ENV_ARG_LIMIT 146 int 147 default 32 if !UML 148 default 128 if UML 149 help 150 Maximum of each of the number of arguments and environment 151 variables passed to init from the kernel command line. 152 153config COMPILE_TEST 154 bool "Compile also drivers which will not load" 155 depends on HAS_IOMEM 156 help 157 Some drivers can be compiled on a different platform than they are 158 intended to be run on. Despite they cannot be loaded there (or even 159 when they load they cannot be used due to missing HW support), 160 developers still, opposing to distributors, might want to build such 161 drivers to compile-test them. 162 163 If you are a developer and want to build everything available, say Y 164 here. If you are a user/distributor, say N here to exclude useless 165 drivers to be distributed. 166 167config WERROR 168 bool "Compile the kernel with warnings as errors" 169 default COMPILE_TEST 170 help 171 A kernel build should not cause any compiler warnings, and this 172 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 173 to enforce that rule by default. Certain warnings from other tools 174 such as the linker may be upgraded to errors with this option as 175 well. 176 177 However, if you have a new (or very old) compiler or linker with odd 178 and unusual warnings, or you have some architecture with problems, 179 you may need to disable this config option in order to 180 successfully build the kernel. 181 182 If in doubt, say Y. 183 184config UAPI_HEADER_TEST 185 bool "Compile test UAPI headers" 186 depends on HEADERS_INSTALL && CC_CAN_LINK 187 help 188 Compile test headers exported to user-space to ensure they are 189 self-contained, i.e. compilable as standalone units. 190 191 If you are a developer or tester and want to ensure the exported 192 headers are self-contained, say Y here. Otherwise, choose N. 193 194config LOCALVERSION 195 string "Local version - append to kernel release" 196 help 197 Append an extra string to the end of your kernel version. 198 This will show up when you type uname, for example. 199 The string you set here will be appended after the contents of 200 any files with a filename matching localversion* in your 201 object and source tree, in that order. Your total string can 202 be a maximum of 64 characters. 203 204config LOCALVERSION_AUTO 205 bool "Automatically append version information to the version string" 206 default y 207 depends on !COMPILE_TEST 208 help 209 This will try to automatically determine if the current tree is a 210 release tree by looking for git tags that belong to the current 211 top of tree revision. 212 213 A string of the format -gxxxxxxxx will be added to the localversion 214 if a git-based tree is found. The string generated by this will be 215 appended after any matching localversion* files, and after the value 216 set in CONFIG_LOCALVERSION. 217 218 (The actual string used here is the first 12 characters produced 219 by running the command: 220 221 $ git rev-parse --verify HEAD 222 223 which is done within the script "scripts/setlocalversion".) 224 225config BUILD_SALT 226 string "Build ID Salt" 227 default "" 228 help 229 The build ID is used to link binaries and their debug info. Setting 230 this option will use the value in the calculation of the build id. 231 This is mostly useful for distributions which want to ensure the 232 build is unique between builds. It's safe to leave the default. 233 234config HAVE_KERNEL_GZIP 235 bool 236 237config HAVE_KERNEL_BZIP2 238 bool 239 240config HAVE_KERNEL_LZMA 241 bool 242 243config HAVE_KERNEL_XZ 244 bool 245 246config HAVE_KERNEL_LZO 247 bool 248 249config HAVE_KERNEL_LZ4 250 bool 251 252config HAVE_KERNEL_ZSTD 253 bool 254 255config HAVE_KERNEL_UNCOMPRESSED 256 bool 257 258choice 259 prompt "Kernel compression mode" 260 default KERNEL_GZIP 261 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED 262 help 263 The linux kernel is a kind of self-extracting executable. 264 Several compression algorithms are available, which differ 265 in efficiency, compression and decompression speed. 266 Compression speed is only relevant when building a kernel. 267 Decompression speed is relevant at each boot. 268 269 If you have any problems with bzip2 or lzma compressed 270 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 271 version of this functionality (bzip2 only), for 2.4, was 272 supplied by Christian Ludwig) 273 274 High compression options are mostly useful for users, who 275 are low on disk space (embedded systems), but for whom ram 276 size matters less. 277 278 If in doubt, select 'gzip' 279 280config KERNEL_GZIP 281 bool "Gzip" 282 depends on HAVE_KERNEL_GZIP 283 help 284 The old and tried gzip compression. It provides a good balance 285 between compression ratio and decompression speed. 286 287config KERNEL_BZIP2 288 bool "Bzip2" 289 depends on HAVE_KERNEL_BZIP2 290 help 291 Its compression ratio and speed is intermediate. 292 Decompression speed is slowest among the choices. The kernel 293 size is about 10% smaller with bzip2, in comparison to gzip. 294 Bzip2 uses a large amount of memory. For modern kernels you 295 will need at least 8MB RAM or more for booting. 296 297config KERNEL_LZMA 298 bool "LZMA" 299 depends on HAVE_KERNEL_LZMA 300 help 301 This compression algorithm's ratio is best. Decompression speed 302 is between gzip and bzip2. Compression is slowest. 303 The kernel size is about 33% smaller with LZMA in comparison to gzip. 304 305config KERNEL_XZ 306 bool "XZ" 307 depends on HAVE_KERNEL_XZ 308 help 309 XZ uses the LZMA2 algorithm and instruction set specific 310 BCJ filters which can improve compression ratio of executable 311 code. The size of the kernel is about 30% smaller with XZ in 312 comparison to gzip. On architectures for which there is a BCJ 313 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 314 will create a few percent smaller kernel than plain LZMA. 315 316 The speed is about the same as with LZMA: The decompression 317 speed of XZ is better than that of bzip2 but worse than gzip 318 and LZO. Compression is slow. 319 320config KERNEL_LZO 321 bool "LZO" 322 depends on HAVE_KERNEL_LZO 323 help 324 Its compression ratio is the poorest among the choices. The kernel 325 size is about 10% bigger than gzip; however its speed 326 (both compression and decompression) is the fastest. 327 328config KERNEL_LZ4 329 bool "LZ4" 330 depends on HAVE_KERNEL_LZ4 331 help 332 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 333 A preliminary version of LZ4 de/compression tool is available at 334 <https://code.google.com/p/lz4/>. 335 336 Its compression ratio is worse than LZO. The size of the kernel 337 is about 8% bigger than LZO. But the decompression speed is 338 faster than LZO. 339 340config KERNEL_ZSTD 341 bool "ZSTD" 342 depends on HAVE_KERNEL_ZSTD 343 help 344 ZSTD is a compression algorithm targeting intermediate compression 345 with fast decompression speed. It will compress better than GZIP and 346 decompress around the same speed as LZO, but slower than LZ4. You 347 will need at least 192 KB RAM or more for booting. The zstd command 348 line tool is required for compression. 349 350config KERNEL_UNCOMPRESSED 351 bool "None" 352 depends on HAVE_KERNEL_UNCOMPRESSED 353 help 354 Produce uncompressed kernel image. This option is usually not what 355 you want. It is useful for debugging the kernel in slow simulation 356 environments, where decompressing and moving the kernel is awfully 357 slow. This option allows early boot code to skip the decompressor 358 and jump right at uncompressed kernel image. 359 360endchoice 361 362config DEFAULT_INIT 363 string "Default init path" 364 default "" 365 help 366 This option determines the default init for the system if no init= 367 option is passed on the kernel command line. If the requested path is 368 not present, we will still then move on to attempting further 369 locations (e.g. /sbin/init, etc). If this is empty, we will just use 370 the fallback list when init= is not passed. 371 372config DEFAULT_HOSTNAME 373 string "Default hostname" 374 default "(none)" 375 help 376 This option determines the default system hostname before userspace 377 calls sethostname(2). The kernel traditionally uses "(none)" here, 378 but you may wish to use a different default here to make a minimal 379 system more usable with less configuration. 380 381config SYSVIPC 382 bool "System V IPC" 383 help 384 Inter Process Communication is a suite of library functions and 385 system calls which let processes (running programs) synchronize and 386 exchange information. It is generally considered to be a good thing, 387 and some programs won't run unless you say Y here. In particular, if 388 you want to run the DOS emulator dosemu under Linux (read the 389 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 390 you'll need to say Y here. 391 392 You can find documentation about IPC with "info ipc" and also in 393 section 6.4 of the Linux Programmer's Guide, available from 394 <http://www.tldp.org/guides.html>. 395 396config SYSVIPC_SYSCTL 397 bool 398 depends on SYSVIPC 399 depends on SYSCTL 400 default y 401 402config SYSVIPC_COMPAT 403 def_bool y 404 depends on COMPAT && SYSVIPC 405 406config POSIX_MQUEUE 407 bool "POSIX Message Queues" 408 depends on NET 409 help 410 POSIX variant of message queues is a part of IPC. In POSIX message 411 queues every message has a priority which decides about succession 412 of receiving it by a process. If you want to compile and run 413 programs written e.g. for Solaris with use of its POSIX message 414 queues (functions mq_*) say Y here. 415 416 POSIX message queues are visible as a filesystem called 'mqueue' 417 and can be mounted somewhere if you want to do filesystem 418 operations on message queues. 419 420 If unsure, say Y. 421 422config POSIX_MQUEUE_SYSCTL 423 bool 424 depends on POSIX_MQUEUE 425 depends on SYSCTL 426 default y 427 428config WATCH_QUEUE 429 bool "General notification queue" 430 default n 431 help 432 433 This is a general notification queue for the kernel to pass events to 434 userspace by splicing them into pipes. It can be used in conjunction 435 with watches for key/keyring change notifications and device 436 notifications. 437 438 See Documentation/core-api/watch_queue.rst 439 440config CROSS_MEMORY_ATTACH 441 bool "Enable process_vm_readv/writev syscalls" 442 depends on MMU 443 default y 444 help 445 Enabling this option adds the system calls process_vm_readv and 446 process_vm_writev which allow a process with the correct privileges 447 to directly read from or write to another process' address space. 448 See the man page for more details. 449 450config USELIB 451 bool "uselib syscall (for libc5 and earlier)" 452 default ALPHA || M68K || SPARC 453 help 454 This option enables the uselib syscall, a system call used in the 455 dynamic linker from libc5 and earlier. glibc does not use this 456 system call. If you intend to run programs built on libc5 or 457 earlier, you may need to enable this syscall. Current systems 458 running glibc can safely disable this. 459 460config AUDIT 461 bool "Auditing support" 462 depends on NET 463 help 464 Enable auditing infrastructure that can be used with another 465 kernel subsystem, such as SELinux (which requires this for 466 logging of avc messages output). System call auditing is included 467 on architectures which support it. 468 469config HAVE_ARCH_AUDITSYSCALL 470 bool 471 472config AUDITSYSCALL 473 def_bool y 474 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 475 select FSNOTIFY 476 477source "kernel/irq/Kconfig" 478source "kernel/time/Kconfig" 479source "kernel/bpf/Kconfig" 480source "kernel/Kconfig.preempt" 481 482menu "CPU/Task time and stats accounting" 483 484config VIRT_CPU_ACCOUNTING 485 bool 486 487choice 488 prompt "Cputime accounting" 489 default TICK_CPU_ACCOUNTING 490 491# Kind of a stub config for the pure tick based cputime accounting 492config TICK_CPU_ACCOUNTING 493 bool "Simple tick based cputime accounting" 494 depends on !S390 && !NO_HZ_FULL 495 help 496 This is the basic tick based cputime accounting that maintains 497 statistics about user, system and idle time spent on per jiffies 498 granularity. 499 500 If unsure, say Y. 501 502config VIRT_CPU_ACCOUNTING_NATIVE 503 bool "Deterministic task and CPU time accounting" 504 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 505 select VIRT_CPU_ACCOUNTING 506 help 507 Select this option to enable more accurate task and CPU time 508 accounting. This is done by reading a CPU counter on each 509 kernel entry and exit and on transitions within the kernel 510 between system, softirq and hardirq state, so there is a 511 small performance impact. In the case of s390 or IBM POWER > 5, 512 this also enables accounting of stolen time on logically-partitioned 513 systems. 514 515config VIRT_CPU_ACCOUNTING_GEN 516 bool "Full dynticks CPU time accounting" 517 depends on HAVE_CONTEXT_TRACKING_USER 518 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 519 depends on GENERIC_CLOCKEVENTS 520 select VIRT_CPU_ACCOUNTING 521 select CONTEXT_TRACKING_USER 522 help 523 Select this option to enable task and CPU time accounting on full 524 dynticks systems. This accounting is implemented by watching every 525 kernel-user boundaries using the context tracking subsystem. 526 The accounting is thus performed at the expense of some significant 527 overhead. 528 529 For now this is only useful if you are working on the full 530 dynticks subsystem development. 531 532 If unsure, say N. 533 534endchoice 535 536config IRQ_TIME_ACCOUNTING 537 bool "Fine granularity task level IRQ time accounting" 538 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 539 help 540 Select this option to enable fine granularity task irq time 541 accounting. This is done by reading a timestamp on each 542 transitions between softirq and hardirq state, so there can be a 543 small performance impact. 544 545 If in doubt, say N here. 546 547config HAVE_SCHED_AVG_IRQ 548 def_bool y 549 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 550 depends on SMP 551 552config SCHED_HW_PRESSURE 553 bool 554 default y if ARM && ARM_CPU_TOPOLOGY 555 default y if ARM64 556 depends on SMP 557 depends on CPU_FREQ_THERMAL 558 help 559 Select this option to enable HW pressure accounting in the 560 scheduler. HW pressure is the value conveyed to the scheduler 561 that reflects the reduction in CPU compute capacity resulted from 562 HW throttling. HW throttling occurs when the performance of 563 a CPU is capped due to high operating temperatures as an example. 564 565 If selected, the scheduler will be able to balance tasks accordingly, 566 i.e. put less load on throttled CPUs than on non/less throttled ones. 567 568 This requires the architecture to implement 569 arch_update_hw_pressure() and arch_scale_thermal_pressure(). 570 571config BSD_PROCESS_ACCT 572 bool "BSD Process Accounting" 573 depends on MULTIUSER 574 help 575 If you say Y here, a user level program will be able to instruct the 576 kernel (via a special system call) to write process accounting 577 information to a file: whenever a process exits, information about 578 that process will be appended to the file by the kernel. The 579 information includes things such as creation time, owning user, 580 command name, memory usage, controlling terminal etc. (the complete 581 list is in the struct acct in <file:include/linux/acct.h>). It is 582 up to the user level program to do useful things with this 583 information. This is generally a good idea, so say Y. 584 585config BSD_PROCESS_ACCT_V3 586 bool "BSD Process Accounting version 3 file format" 587 depends on BSD_PROCESS_ACCT 588 default n 589 help 590 If you say Y here, the process accounting information is written 591 in a new file format that also logs the process IDs of each 592 process and its parent. Note that this file format is incompatible 593 with previous v0/v1/v2 file formats, so you will need updated tools 594 for processing it. A preliminary version of these tools is available 595 at <http://www.gnu.org/software/acct/>. 596 597config TASKSTATS 598 bool "Export task/process statistics through netlink" 599 depends on NET 600 depends on MULTIUSER 601 default n 602 help 603 Export selected statistics for tasks/processes through the 604 generic netlink interface. Unlike BSD process accounting, the 605 statistics are available during the lifetime of tasks/processes as 606 responses to commands. Like BSD accounting, they are sent to user 607 space on task exit. 608 609 Say N if unsure. 610 611config TASK_DELAY_ACCT 612 bool "Enable per-task delay accounting" 613 depends on TASKSTATS 614 select SCHED_INFO 615 help 616 Collect information on time spent by a task waiting for system 617 resources like cpu, synchronous block I/O completion and swapping 618 in pages. Such statistics can help in setting a task's priorities 619 relative to other tasks for cpu, io, rss limits etc. 620 621 Say N if unsure. 622 623config TASK_XACCT 624 bool "Enable extended accounting over taskstats" 625 depends on TASKSTATS 626 help 627 Collect extended task accounting data and send the data 628 to userland for processing over the taskstats interface. 629 630 Say N if unsure. 631 632config TASK_IO_ACCOUNTING 633 bool "Enable per-task storage I/O accounting" 634 depends on TASK_XACCT 635 help 636 Collect information on the number of bytes of storage I/O which this 637 task has caused. 638 639 Say N if unsure. 640 641config PSI 642 bool "Pressure stall information tracking" 643 select KERNFS 644 help 645 Collect metrics that indicate how overcommitted the CPU, memory, 646 and IO capacity are in the system. 647 648 If you say Y here, the kernel will create /proc/pressure/ with the 649 pressure statistics files cpu, memory, and io. These will indicate 650 the share of walltime in which some or all tasks in the system are 651 delayed due to contention of the respective resource. 652 653 In kernels with cgroup support, cgroups (cgroup2 only) will 654 have cpu.pressure, memory.pressure, and io.pressure files, 655 which aggregate pressure stalls for the grouped tasks only. 656 657 For more details see Documentation/accounting/psi.rst. 658 659 Say N if unsure. 660 661config PSI_DEFAULT_DISABLED 662 bool "Require boot parameter to enable pressure stall information tracking" 663 default n 664 depends on PSI 665 help 666 If set, pressure stall information tracking will be disabled 667 per default but can be enabled through passing psi=1 on the 668 kernel commandline during boot. 669 670 This feature adds some code to the task wakeup and sleep 671 paths of the scheduler. The overhead is too low to affect 672 common scheduling-intense workloads in practice (such as 673 webservers, memcache), but it does show up in artificial 674 scheduler stress tests, such as hackbench. 675 676 If you are paranoid and not sure what the kernel will be 677 used for, say Y. 678 679 Say N if unsure. 680 681endmenu # "CPU/Task time and stats accounting" 682 683config CPU_ISOLATION 684 bool "CPU isolation" 685 depends on SMP || COMPILE_TEST 686 default y 687 help 688 Make sure that CPUs running critical tasks are not disturbed by 689 any source of "noise" such as unbound workqueues, timers, kthreads... 690 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 691 the "isolcpus=" boot parameter. 692 693 Say Y if unsure. 694 695source "kernel/rcu/Kconfig" 696 697config IKCONFIG 698 tristate "Kernel .config support" 699 help 700 This option enables the complete Linux kernel ".config" file 701 contents to be saved in the kernel. It provides documentation 702 of which kernel options are used in a running kernel or in an 703 on-disk kernel. This information can be extracted from the kernel 704 image file with the script scripts/extract-ikconfig and used as 705 input to rebuild the current kernel or to build another kernel. 706 It can also be extracted from a running kernel by reading 707 /proc/config.gz if enabled (below). 708 709config IKCONFIG_PROC 710 bool "Enable access to .config through /proc/config.gz" 711 depends on IKCONFIG && PROC_FS 712 help 713 This option enables access to the kernel configuration file 714 through /proc/config.gz. 715 716config IKHEADERS 717 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 718 depends on SYSFS 719 help 720 This option enables access to the in-kernel headers that are generated during 721 the build process. These can be used to build eBPF tracing programs, 722 or similar programs. If you build the headers as a module, a module called 723 kheaders.ko is built which can be loaded on-demand to get access to headers. 724 725config LOG_BUF_SHIFT 726 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 727 range 12 25 728 default 17 729 depends on PRINTK 730 help 731 Select the minimal kernel log buffer size as a power of 2. 732 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 733 parameter, see below. Any higher size also might be forced 734 by "log_buf_len" boot parameter. 735 736 Examples: 737 17 => 128 KB 738 16 => 64 KB 739 15 => 32 KB 740 14 => 16 KB 741 13 => 8 KB 742 12 => 4 KB 743 744config LOG_CPU_MAX_BUF_SHIFT 745 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 746 depends on SMP 747 range 0 21 748 default 0 if BASE_SMALL 749 default 12 750 depends on PRINTK 751 help 752 This option allows to increase the default ring buffer size 753 according to the number of CPUs. The value defines the contribution 754 of each CPU as a power of 2. The used space is typically only few 755 lines however it might be much more when problems are reported, 756 e.g. backtraces. 757 758 The increased size means that a new buffer has to be allocated and 759 the original static one is unused. It makes sense only on systems 760 with more CPUs. Therefore this value is used only when the sum of 761 contributions is greater than the half of the default kernel ring 762 buffer as defined by LOG_BUF_SHIFT. The default values are set 763 so that more than 16 CPUs are needed to trigger the allocation. 764 765 Also this option is ignored when "log_buf_len" kernel parameter is 766 used as it forces an exact (power of two) size of the ring buffer. 767 768 The number of possible CPUs is used for this computation ignoring 769 hotplugging making the computation optimal for the worst case 770 scenario while allowing a simple algorithm to be used from bootup. 771 772 Examples shift values and their meaning: 773 17 => 128 KB for each CPU 774 16 => 64 KB for each CPU 775 15 => 32 KB for each CPU 776 14 => 16 KB for each CPU 777 13 => 8 KB for each CPU 778 12 => 4 KB for each CPU 779 780config PRINTK_INDEX 781 bool "Printk indexing debugfs interface" 782 depends on PRINTK && DEBUG_FS 783 help 784 Add support for indexing of all printk formats known at compile time 785 at <debugfs>/printk/index/<module>. 786 787 This can be used as part of maintaining daemons which monitor 788 /dev/kmsg, as it permits auditing the printk formats present in a 789 kernel, allowing detection of cases where monitored printks are 790 changed or no longer present. 791 792 There is no additional runtime cost to printk with this enabled. 793 794# 795# Architectures with an unreliable sched_clock() should select this: 796# 797config HAVE_UNSTABLE_SCHED_CLOCK 798 bool 799 800config GENERIC_SCHED_CLOCK 801 bool 802 803menu "Scheduler features" 804 805config UCLAMP_TASK 806 bool "Enable utilization clamping for RT/FAIR tasks" 807 depends on CPU_FREQ_GOV_SCHEDUTIL 808 help 809 This feature enables the scheduler to track the clamped utilization 810 of each CPU based on RUNNABLE tasks scheduled on that CPU. 811 812 With this option, the user can specify the min and max CPU 813 utilization allowed for RUNNABLE tasks. The max utilization defines 814 the maximum frequency a task should use while the min utilization 815 defines the minimum frequency it should use. 816 817 Both min and max utilization clamp values are hints to the scheduler, 818 aiming at improving its frequency selection policy, but they do not 819 enforce or grant any specific bandwidth for tasks. 820 821 If in doubt, say N. 822 823config UCLAMP_BUCKETS_COUNT 824 int "Number of supported utilization clamp buckets" 825 range 5 20 826 default 5 827 depends on UCLAMP_TASK 828 help 829 Defines the number of clamp buckets to use. The range of each bucket 830 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 831 number of clamp buckets the finer their granularity and the higher 832 the precision of clamping aggregation and tracking at run-time. 833 834 For example, with the minimum configuration value we will have 5 835 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 836 be refcounted in the [20..39]% bucket and will set the bucket clamp 837 effective value to 25%. 838 If a second 30% boosted task should be co-scheduled on the same CPU, 839 that task will be refcounted in the same bucket of the first task and 840 it will boost the bucket clamp effective value to 30%. 841 The clamp effective value of a bucket is reset to its nominal value 842 (20% in the example above) when there are no more tasks refcounted in 843 that bucket. 844 845 An additional boost/capping margin can be added to some tasks. In the 846 example above the 25% task will be boosted to 30% until it exits the 847 CPU. If that should be considered not acceptable on certain systems, 848 it's always possible to reduce the margin by increasing the number of 849 clamp buckets to trade off used memory for run-time tracking 850 precision. 851 852 If in doubt, use the default value. 853 854endmenu 855 856# 857# For architectures that want to enable the support for NUMA-affine scheduler 858# balancing logic: 859# 860config ARCH_SUPPORTS_NUMA_BALANCING 861 bool 862 863# 864# For architectures that prefer to flush all TLBs after a number of pages 865# are unmapped instead of sending one IPI per page to flush. The architecture 866# must provide guarantees on what happens if a clean TLB cache entry is 867# written after the unmap. Details are in mm/rmap.c near the check for 868# should_defer_flush. The architecture should also consider if the full flush 869# and the refill costs are offset by the savings of sending fewer IPIs. 870config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 871 bool 872 873config CC_HAS_INT128 874 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 875 876config CC_IMPLICIT_FALLTHROUGH 877 string 878 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 879 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 880 881# Currently, disable gcc-10+ array-bounds globally. 882# It's still broken in gcc-13, so no upper bound yet. 883config GCC10_NO_ARRAY_BOUNDS 884 def_bool y 885 886config CC_NO_ARRAY_BOUNDS 887 bool 888 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS 889 890# Currently, disable -Wstringop-overflow for GCC globally. 891config GCC_NO_STRINGOP_OVERFLOW 892 def_bool y 893 894config CC_NO_STRINGOP_OVERFLOW 895 bool 896 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 897 898config CC_STRINGOP_OVERFLOW 899 bool 900 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 901 902# 903# For architectures that know their GCC __int128 support is sound 904# 905config ARCH_SUPPORTS_INT128 906 bool 907 908# For architectures that (ab)use NUMA to represent different memory regions 909# all cpu-local but of different latencies, such as SuperH. 910# 911config ARCH_WANT_NUMA_VARIABLE_LOCALITY 912 bool 913 914config NUMA_BALANCING 915 bool "Memory placement aware NUMA scheduler" 916 depends on ARCH_SUPPORTS_NUMA_BALANCING 917 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 918 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 919 help 920 This option adds support for automatic NUMA aware memory/task placement. 921 The mechanism is quite primitive and is based on migrating memory when 922 it has references to the node the task is running on. 923 924 This system will be inactive on UMA systems. 925 926config NUMA_BALANCING_DEFAULT_ENABLED 927 bool "Automatically enable NUMA aware memory/task placement" 928 default y 929 depends on NUMA_BALANCING 930 help 931 If set, automatic NUMA balancing will be enabled if running on a NUMA 932 machine. 933 934config SLAB_OBJ_EXT 935 bool 936 937menuconfig CGROUPS 938 bool "Control Group support" 939 select KERNFS 940 help 941 This option adds support for grouping sets of processes together, for 942 use with process control subsystems such as Cpusets, CFS, memory 943 controls or device isolation. 944 See 945 - Documentation/scheduler/sched-design-CFS.rst (CFS) 946 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 947 and resource control) 948 949 Say N if unsure. 950 951if CGROUPS 952 953config PAGE_COUNTER 954 bool 955 956config CGROUP_FAVOR_DYNMODS 957 bool "Favor dynamic modification latency reduction by default" 958 help 959 This option enables the "favordynmods" mount option by default 960 which reduces the latencies of dynamic cgroup modifications such 961 as task migrations and controller on/offs at the cost of making 962 hot path operations such as forks and exits more expensive. 963 964 Say N if unsure. 965 966config MEMCG 967 bool "Memory controller" 968 select PAGE_COUNTER 969 select EVENTFD 970 select SLAB_OBJ_EXT 971 help 972 Provides control over the memory footprint of tasks in a cgroup. 973 974config MEMCG_V1 975 bool "Legacy cgroup v1 memory controller" 976 depends on MEMCG 977 default n 978 help 979 Legacy cgroup v1 memory controller which has been deprecated by 980 cgroup v2 implementation. The v1 is there for legacy applications 981 which haven't migrated to the new cgroup v2 interface yet. If you 982 do not have any such application then you are completely fine leaving 983 this option disabled. 984 985 Please note that feature set of the legacy memory controller is likely 986 going to shrink due to deprecation process. New deployments with v1 987 controller are highly discouraged. 988 989 San N is unsure. 990 991config BLK_CGROUP 992 bool "IO controller" 993 depends on BLOCK 994 default n 995 help 996 Generic block IO controller cgroup interface. This is the common 997 cgroup interface which should be used by various IO controlling 998 policies. 999 1000 Currently, CFQ IO scheduler uses it to recognize task groups and 1001 control disk bandwidth allocation (proportional time slice allocation) 1002 to such task groups. It is also used by bio throttling logic in 1003 block layer to implement upper limit in IO rates on a device. 1004 1005 This option only enables generic Block IO controller infrastructure. 1006 One needs to also enable actual IO controlling logic/policy. For 1007 enabling proportional weight division of disk bandwidth in CFQ, set 1008 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1009 CONFIG_BLK_DEV_THROTTLING=y. 1010 1011 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1012 1013config CGROUP_WRITEBACK 1014 bool 1015 depends on MEMCG && BLK_CGROUP 1016 default y 1017 1018menuconfig CGROUP_SCHED 1019 bool "CPU controller" 1020 default n 1021 help 1022 This feature lets CPU scheduler recognize task groups and control CPU 1023 bandwidth allocation to such task groups. It uses cgroups to group 1024 tasks. 1025 1026if CGROUP_SCHED 1027config FAIR_GROUP_SCHED 1028 bool "Group scheduling for SCHED_OTHER" 1029 depends on CGROUP_SCHED 1030 default CGROUP_SCHED 1031 1032config CFS_BANDWIDTH 1033 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1034 depends on FAIR_GROUP_SCHED 1035 default n 1036 help 1037 This option allows users to define CPU bandwidth rates (limits) for 1038 tasks running within the fair group scheduler. Groups with no limit 1039 set are considered to be unconstrained and will run with no 1040 restriction. 1041 See Documentation/scheduler/sched-bwc.rst for more information. 1042 1043config RT_GROUP_SCHED 1044 bool "Group scheduling for SCHED_RR/FIFO" 1045 depends on CGROUP_SCHED 1046 default n 1047 help 1048 This feature lets you explicitly allocate real CPU bandwidth 1049 to task groups. If enabled, it will also make it impossible to 1050 schedule realtime tasks for non-root users until you allocate 1051 realtime bandwidth for them. 1052 See Documentation/scheduler/sched-rt-group.rst for more information. 1053 1054endif #CGROUP_SCHED 1055 1056config SCHED_MM_CID 1057 def_bool y 1058 depends on SMP && RSEQ 1059 1060config UCLAMP_TASK_GROUP 1061 bool "Utilization clamping per group of tasks" 1062 depends on CGROUP_SCHED 1063 depends on UCLAMP_TASK 1064 default n 1065 help 1066 This feature enables the scheduler to track the clamped utilization 1067 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1068 1069 When this option is enabled, the user can specify a min and max 1070 CPU bandwidth which is allowed for each single task in a group. 1071 The max bandwidth allows to clamp the maximum frequency a task 1072 can use, while the min bandwidth allows to define a minimum 1073 frequency a task will always use. 1074 1075 When task group based utilization clamping is enabled, an eventually 1076 specified task-specific clamp value is constrained by the cgroup 1077 specified clamp value. Both minimum and maximum task clamping cannot 1078 be bigger than the corresponding clamping defined at task group level. 1079 1080 If in doubt, say N. 1081 1082config CGROUP_PIDS 1083 bool "PIDs controller" 1084 help 1085 Provides enforcement of process number limits in the scope of a 1086 cgroup. Any attempt to fork more processes than is allowed in the 1087 cgroup will fail. PIDs are fundamentally a global resource because it 1088 is fairly trivial to reach PID exhaustion before you reach even a 1089 conservative kmemcg limit. As a result, it is possible to grind a 1090 system to halt without being limited by other cgroup policies. The 1091 PIDs controller is designed to stop this from happening. 1092 1093 It should be noted that organisational operations (such as attaching 1094 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1095 since the PIDs limit only affects a process's ability to fork, not to 1096 attach to a cgroup. 1097 1098config CGROUP_RDMA 1099 bool "RDMA controller" 1100 help 1101 Provides enforcement of RDMA resources defined by IB stack. 1102 It is fairly easy for consumers to exhaust RDMA resources, which 1103 can result into resource unavailability to other consumers. 1104 RDMA controller is designed to stop this from happening. 1105 Attaching processes with active RDMA resources to the cgroup 1106 hierarchy is allowed even if can cross the hierarchy's limit. 1107 1108config CGROUP_FREEZER 1109 bool "Freezer controller" 1110 help 1111 Provides a way to freeze and unfreeze all tasks in a 1112 cgroup. 1113 1114 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1115 controller includes important in-kernel memory consumers per default. 1116 1117 If you're using cgroup2, say N. 1118 1119config CGROUP_HUGETLB 1120 bool "HugeTLB controller" 1121 depends on HUGETLB_PAGE 1122 select PAGE_COUNTER 1123 default n 1124 help 1125 Provides a cgroup controller for HugeTLB pages. 1126 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1127 The limit is enforced during page fault. Since HugeTLB doesn't 1128 support page reclaim, enforcing the limit at page fault time implies 1129 that, the application will get SIGBUS signal if it tries to access 1130 HugeTLB pages beyond its limit. This requires the application to know 1131 beforehand how much HugeTLB pages it would require for its use. The 1132 control group is tracked in the third page lru pointer. This means 1133 that we cannot use the controller with huge page less than 3 pages. 1134 1135config CPUSETS 1136 bool "Cpuset controller" 1137 depends on SMP 1138 help 1139 This option will let you create and manage CPUSETs which 1140 allow dynamically partitioning a system into sets of CPUs and 1141 Memory Nodes and assigning tasks to run only within those sets. 1142 This is primarily useful on large SMP or NUMA systems. 1143 1144 Say N if unsure. 1145 1146config CPUSETS_V1 1147 bool "Legacy cgroup v1 cpusets controller" 1148 depends on CPUSETS 1149 default n 1150 help 1151 Legacy cgroup v1 cpusets controller which has been deprecated by 1152 cgroup v2 implementation. The v1 is there for legacy applications 1153 which haven't migrated to the new cgroup v2 interface yet. If you 1154 do not have any such application then you are completely fine leaving 1155 this option disabled. 1156 1157 Say N if unsure. 1158 1159config PROC_PID_CPUSET 1160 bool "Include legacy /proc/<pid>/cpuset file" 1161 depends on CPUSETS 1162 default y 1163 1164config CGROUP_DEVICE 1165 bool "Device controller" 1166 help 1167 Provides a cgroup controller implementing whitelists for 1168 devices which a process in the cgroup can mknod or open. 1169 1170config CGROUP_CPUACCT 1171 bool "Simple CPU accounting controller" 1172 help 1173 Provides a simple controller for monitoring the 1174 total CPU consumed by the tasks in a cgroup. 1175 1176config CGROUP_PERF 1177 bool "Perf controller" 1178 depends on PERF_EVENTS 1179 help 1180 This option extends the perf per-cpu mode to restrict monitoring 1181 to threads which belong to the cgroup specified and run on the 1182 designated cpu. Or this can be used to have cgroup ID in samples 1183 so that it can monitor performance events among cgroups. 1184 1185 Say N if unsure. 1186 1187config CGROUP_BPF 1188 bool "Support for eBPF programs attached to cgroups" 1189 depends on BPF_SYSCALL 1190 select SOCK_CGROUP_DATA 1191 help 1192 Allow attaching eBPF programs to a cgroup using the bpf(2) 1193 syscall command BPF_PROG_ATTACH. 1194 1195 In which context these programs are accessed depends on the type 1196 of attachment. For instance, programs that are attached using 1197 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1198 inet sockets. 1199 1200config CGROUP_MISC 1201 bool "Misc resource controller" 1202 default n 1203 help 1204 Provides a controller for miscellaneous resources on a host. 1205 1206 Miscellaneous scalar resources are the resources on the host system 1207 which cannot be abstracted like the other cgroups. This controller 1208 tracks and limits the miscellaneous resources used by a process 1209 attached to a cgroup hierarchy. 1210 1211 For more information, please check misc cgroup section in 1212 /Documentation/admin-guide/cgroup-v2.rst. 1213 1214config CGROUP_DEBUG 1215 bool "Debug controller" 1216 default n 1217 depends on DEBUG_KERNEL 1218 help 1219 This option enables a simple controller that exports 1220 debugging information about the cgroups framework. This 1221 controller is for control cgroup debugging only. Its 1222 interfaces are not stable. 1223 1224 Say N. 1225 1226config SOCK_CGROUP_DATA 1227 bool 1228 default n 1229 1230endif # CGROUPS 1231 1232menuconfig NAMESPACES 1233 bool "Namespaces support" if EXPERT 1234 depends on MULTIUSER 1235 default !EXPERT 1236 help 1237 Provides the way to make tasks work with different objects using 1238 the same id. For example same IPC id may refer to different objects 1239 or same user id or pid may refer to different tasks when used in 1240 different namespaces. 1241 1242if NAMESPACES 1243 1244config UTS_NS 1245 bool "UTS namespace" 1246 default y 1247 help 1248 In this namespace tasks see different info provided with the 1249 uname() system call 1250 1251config TIME_NS 1252 bool "TIME namespace" 1253 depends on GENERIC_VDSO_TIME_NS 1254 default y 1255 help 1256 In this namespace boottime and monotonic clocks can be set. 1257 The time will keep going with the same pace. 1258 1259config IPC_NS 1260 bool "IPC namespace" 1261 depends on (SYSVIPC || POSIX_MQUEUE) 1262 default y 1263 help 1264 In this namespace tasks work with IPC ids which correspond to 1265 different IPC objects in different namespaces. 1266 1267config USER_NS 1268 bool "User namespace" 1269 default n 1270 help 1271 This allows containers, i.e. vservers, to use user namespaces 1272 to provide different user info for different servers. 1273 1274 When user namespaces are enabled in the kernel it is 1275 recommended that the MEMCG option also be enabled and that 1276 user-space use the memory control groups to limit the amount 1277 of memory a memory unprivileged users can use. 1278 1279 If unsure, say N. 1280 1281config PID_NS 1282 bool "PID Namespaces" 1283 default y 1284 help 1285 Support process id namespaces. This allows having multiple 1286 processes with the same pid as long as they are in different 1287 pid namespaces. This is a building block of containers. 1288 1289config NET_NS 1290 bool "Network namespace" 1291 depends on NET 1292 default y 1293 help 1294 Allow user space to create what appear to be multiple instances 1295 of the network stack. 1296 1297endif # NAMESPACES 1298 1299config CHECKPOINT_RESTORE 1300 bool "Checkpoint/restore support" 1301 depends on PROC_FS 1302 select PROC_CHILDREN 1303 select KCMP 1304 default n 1305 help 1306 Enables additional kernel features in a sake of checkpoint/restore. 1307 In particular it adds auxiliary prctl codes to setup process text, 1308 data and heap segment sizes, and a few additional /proc filesystem 1309 entries. 1310 1311 If unsure, say N here. 1312 1313config SCHED_AUTOGROUP 1314 bool "Automatic process group scheduling" 1315 select CGROUPS 1316 select CGROUP_SCHED 1317 select FAIR_GROUP_SCHED 1318 help 1319 This option optimizes the scheduler for common desktop workloads by 1320 automatically creating and populating task groups. This separation 1321 of workloads isolates aggressive CPU burners (like build jobs) from 1322 desktop applications. Task group autogeneration is currently based 1323 upon task session. 1324 1325config RELAY 1326 bool "Kernel->user space relay support (formerly relayfs)" 1327 select IRQ_WORK 1328 help 1329 This option enables support for relay interface support in 1330 certain file systems (such as debugfs). 1331 It is designed to provide an efficient mechanism for tools and 1332 facilities to relay large amounts of data from kernel space to 1333 user space. 1334 1335 If unsure, say N. 1336 1337config BLK_DEV_INITRD 1338 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1339 help 1340 The initial RAM filesystem is a ramfs which is loaded by the 1341 boot loader (loadlin or lilo) and that is mounted as root 1342 before the normal boot procedure. It is typically used to 1343 load modules needed to mount the "real" root file system, 1344 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1345 1346 If RAM disk support (BLK_DEV_RAM) is also included, this 1347 also enables initial RAM disk (initrd) support and adds 1348 15 Kbytes (more on some other architectures) to the kernel size. 1349 1350 If unsure say Y. 1351 1352if BLK_DEV_INITRD 1353 1354source "usr/Kconfig" 1355 1356endif 1357 1358config BOOT_CONFIG 1359 bool "Boot config support" 1360 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1361 help 1362 Extra boot config allows system admin to pass a config file as 1363 complemental extension of kernel cmdline when booting. 1364 The boot config file must be attached at the end of initramfs 1365 with checksum, size and magic word. 1366 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1367 1368 If unsure, say Y. 1369 1370config BOOT_CONFIG_FORCE 1371 bool "Force unconditional bootconfig processing" 1372 depends on BOOT_CONFIG 1373 default y if BOOT_CONFIG_EMBED 1374 help 1375 With this Kconfig option set, BOOT_CONFIG processing is carried 1376 out even when the "bootconfig" kernel-boot parameter is omitted. 1377 In fact, with this Kconfig option set, there is no way to 1378 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1379 parameters. 1380 1381 If unsure, say N. 1382 1383config BOOT_CONFIG_EMBED 1384 bool "Embed bootconfig file in the kernel" 1385 depends on BOOT_CONFIG 1386 help 1387 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1388 kernel. Usually, the bootconfig file is loaded with the initrd 1389 image. But if the system doesn't support initrd, this option will 1390 help you by embedding a bootconfig file while building the kernel. 1391 1392 If unsure, say N. 1393 1394config BOOT_CONFIG_EMBED_FILE 1395 string "Embedded bootconfig file path" 1396 depends on BOOT_CONFIG_EMBED 1397 help 1398 Specify a bootconfig file which will be embedded to the kernel. 1399 This bootconfig will be used if there is no initrd or no other 1400 bootconfig in the initrd. 1401 1402config INITRAMFS_PRESERVE_MTIME 1403 bool "Preserve cpio archive mtimes in initramfs" 1404 default y 1405 help 1406 Each entry in an initramfs cpio archive carries an mtime value. When 1407 enabled, extracted cpio items take this mtime, with directory mtime 1408 setting deferred until after creation of any child entries. 1409 1410 If unsure, say Y. 1411 1412choice 1413 prompt "Compiler optimization level" 1414 default CC_OPTIMIZE_FOR_PERFORMANCE 1415 1416config CC_OPTIMIZE_FOR_PERFORMANCE 1417 bool "Optimize for performance (-O2)" 1418 help 1419 This is the default optimization level for the kernel, building 1420 with the "-O2" compiler flag for best performance and most 1421 helpful compile-time warnings. 1422 1423config CC_OPTIMIZE_FOR_SIZE 1424 bool "Optimize for size (-Os)" 1425 help 1426 Choosing this option will pass "-Os" to your compiler resulting 1427 in a smaller kernel. 1428 1429endchoice 1430 1431config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1432 bool 1433 help 1434 This requires that the arch annotates or otherwise protects 1435 its external entry points from being discarded. Linker scripts 1436 must also merge .text.*, .data.*, and .bss.* correctly into 1437 output sections. Care must be taken not to pull in unrelated 1438 sections (e.g., '.text.init'). Typically '.' in section names 1439 is used to distinguish them from label names / C identifiers. 1440 1441config LD_DEAD_CODE_DATA_ELIMINATION 1442 bool "Dead code and data elimination (EXPERIMENTAL)" 1443 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1444 depends on EXPERT 1445 depends on $(cc-option,-ffunction-sections -fdata-sections) 1446 depends on $(ld-option,--gc-sections) 1447 help 1448 Enable this if you want to do dead code and data elimination with 1449 the linker by compiling with -ffunction-sections -fdata-sections, 1450 and linking with --gc-sections. 1451 1452 This can reduce on disk and in-memory size of the kernel 1453 code and static data, particularly for small configs and 1454 on small systems. This has the possibility of introducing 1455 silently broken kernel if the required annotations are not 1456 present. This option is not well tested yet, so use at your 1457 own risk. 1458 1459config LD_ORPHAN_WARN 1460 def_bool y 1461 depends on ARCH_WANT_LD_ORPHAN_WARN 1462 depends on $(ld-option,--orphan-handling=warn) 1463 depends on $(ld-option,--orphan-handling=error) 1464 1465config LD_ORPHAN_WARN_LEVEL 1466 string 1467 depends on LD_ORPHAN_WARN 1468 default "error" if WERROR 1469 default "warn" 1470 1471config SYSCTL 1472 bool 1473 1474config HAVE_UID16 1475 bool 1476 1477config SYSCTL_EXCEPTION_TRACE 1478 bool 1479 help 1480 Enable support for /proc/sys/debug/exception-trace. 1481 1482config SYSCTL_ARCH_UNALIGN_NO_WARN 1483 bool 1484 help 1485 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1486 Allows arch to define/use @no_unaligned_warning to possibly warn 1487 about unaligned access emulation going on under the hood. 1488 1489config SYSCTL_ARCH_UNALIGN_ALLOW 1490 bool 1491 help 1492 Enable support for /proc/sys/kernel/unaligned-trap 1493 Allows arches to define/use @unaligned_enabled to runtime toggle 1494 the unaligned access emulation. 1495 see arch/parisc/kernel/unaligned.c for reference 1496 1497config HAVE_PCSPKR_PLATFORM 1498 bool 1499 1500menuconfig EXPERT 1501 bool "Configure standard kernel features (expert users)" 1502 # Unhide debug options, to make the on-by-default options visible 1503 select DEBUG_KERNEL 1504 help 1505 This option allows certain base kernel options and settings 1506 to be disabled or tweaked. This is for specialized 1507 environments which can tolerate a "non-standard" kernel. 1508 Only use this if you really know what you are doing. 1509 1510config UID16 1511 bool "Enable 16-bit UID system calls" if EXPERT 1512 depends on HAVE_UID16 && MULTIUSER 1513 default y 1514 help 1515 This enables the legacy 16-bit UID syscall wrappers. 1516 1517config MULTIUSER 1518 bool "Multiple users, groups and capabilities support" if EXPERT 1519 default y 1520 help 1521 This option enables support for non-root users, groups and 1522 capabilities. 1523 1524 If you say N here, all processes will run with UID 0, GID 0, and all 1525 possible capabilities. Saying N here also compiles out support for 1526 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1527 setgid, and capset. 1528 1529 If unsure, say Y here. 1530 1531config SGETMASK_SYSCALL 1532 bool "sgetmask/ssetmask syscalls support" if EXPERT 1533 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1534 help 1535 sys_sgetmask and sys_ssetmask are obsolete system calls 1536 no longer supported in libc but still enabled by default in some 1537 architectures. 1538 1539 If unsure, leave the default option here. 1540 1541config SYSFS_SYSCALL 1542 bool "Sysfs syscall support" if EXPERT 1543 default y 1544 help 1545 sys_sysfs is an obsolete system call no longer supported in libc. 1546 Note that disabling this option is more secure but might break 1547 compatibility with some systems. 1548 1549 If unsure say Y here. 1550 1551config FHANDLE 1552 bool "open by fhandle syscalls" if EXPERT 1553 select EXPORTFS 1554 default y 1555 help 1556 If you say Y here, a user level program will be able to map 1557 file names to handle and then later use the handle for 1558 different file system operations. This is useful in implementing 1559 userspace file servers, which now track files using handles instead 1560 of names. The handle would remain the same even if file names 1561 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1562 syscalls. 1563 1564config POSIX_TIMERS 1565 bool "Posix Clocks & timers" if EXPERT 1566 default y 1567 help 1568 This includes native support for POSIX timers to the kernel. 1569 Some embedded systems have no use for them and therefore they 1570 can be configured out to reduce the size of the kernel image. 1571 1572 When this option is disabled, the following syscalls won't be 1573 available: timer_create, timer_gettime: timer_getoverrun, 1574 timer_settime, timer_delete, clock_adjtime, getitimer, 1575 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1576 clock_getres and clock_nanosleep syscalls will be limited to 1577 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1578 1579 If unsure say y. 1580 1581config PRINTK 1582 default y 1583 bool "Enable support for printk" if EXPERT 1584 select IRQ_WORK 1585 help 1586 This option enables normal printk support. Removing it 1587 eliminates most of the message strings from the kernel image 1588 and makes the kernel more or less silent. As this makes it 1589 very difficult to diagnose system problems, saying N here is 1590 strongly discouraged. 1591 1592config BUG 1593 bool "BUG() support" if EXPERT 1594 default y 1595 help 1596 Disabling this option eliminates support for BUG and WARN, reducing 1597 the size of your kernel image and potentially quietly ignoring 1598 numerous fatal conditions. You should only consider disabling this 1599 option for embedded systems with no facilities for reporting errors. 1600 Just say Y. 1601 1602config ELF_CORE 1603 depends on COREDUMP 1604 default y 1605 bool "Enable ELF core dumps" if EXPERT 1606 help 1607 Enable support for generating core dumps. Disabling saves about 4k. 1608 1609 1610config PCSPKR_PLATFORM 1611 bool "Enable PC-Speaker support" if EXPERT 1612 depends on HAVE_PCSPKR_PLATFORM 1613 select I8253_LOCK 1614 default y 1615 help 1616 This option allows to disable the internal PC-Speaker 1617 support, saving some memory. 1618 1619config BASE_SMALL 1620 bool "Enable smaller-sized data structures for core" if EXPERT 1621 help 1622 Enabling this option reduces the size of miscellaneous core 1623 kernel data structures. This saves memory on small machines, 1624 but may reduce performance. 1625 1626config FUTEX 1627 bool "Enable futex support" if EXPERT 1628 depends on !(SPARC32 && SMP) 1629 default y 1630 imply RT_MUTEXES 1631 help 1632 Disabling this option will cause the kernel to be built without 1633 support for "fast userspace mutexes". The resulting kernel may not 1634 run glibc-based applications correctly. 1635 1636config FUTEX_PI 1637 bool 1638 depends on FUTEX && RT_MUTEXES 1639 default y 1640 1641config EPOLL 1642 bool "Enable eventpoll support" if EXPERT 1643 default y 1644 help 1645 Disabling this option will cause the kernel to be built without 1646 support for epoll family of system calls. 1647 1648config SIGNALFD 1649 bool "Enable signalfd() system call" if EXPERT 1650 default y 1651 help 1652 Enable the signalfd() system call that allows to receive signals 1653 on a file descriptor. 1654 1655 If unsure, say Y. 1656 1657config TIMERFD 1658 bool "Enable timerfd() system call" if EXPERT 1659 default y 1660 help 1661 Enable the timerfd() system call that allows to receive timer 1662 events on a file descriptor. 1663 1664 If unsure, say Y. 1665 1666config EVENTFD 1667 bool "Enable eventfd() system call" if EXPERT 1668 default y 1669 help 1670 Enable the eventfd() system call that allows to receive both 1671 kernel notification (ie. KAIO) or userspace notifications. 1672 1673 If unsure, say Y. 1674 1675config SHMEM 1676 bool "Use full shmem filesystem" if EXPERT 1677 default y 1678 depends on MMU 1679 help 1680 The shmem is an internal filesystem used to manage shared memory. 1681 It is backed by swap and manages resource limits. It is also exported 1682 to userspace as tmpfs if TMPFS is enabled. Disabling this 1683 option replaces shmem and tmpfs with the much simpler ramfs code, 1684 which may be appropriate on small systems without swap. 1685 1686config AIO 1687 bool "Enable AIO support" if EXPERT 1688 default y 1689 help 1690 This option enables POSIX asynchronous I/O which may by used 1691 by some high performance threaded applications. Disabling 1692 this option saves about 7k. 1693 1694config IO_URING 1695 bool "Enable IO uring support" if EXPERT 1696 select IO_WQ 1697 default y 1698 help 1699 This option enables support for the io_uring interface, enabling 1700 applications to submit and complete IO through submission and 1701 completion rings that are shared between the kernel and application. 1702 1703config GCOV_PROFILE_URING 1704 bool "Enable GCOV profiling on the io_uring subsystem" 1705 depends on GCOV_KERNEL 1706 help 1707 Enable GCOV profiling on the io_uring subsystem, to facilitate 1708 code coverage testing. 1709 1710 If unsure, say N. 1711 1712 Note that this will have a negative impact on the performance of 1713 the io_uring subsystem, hence this should only be enabled for 1714 specific test purposes. 1715 1716config ADVISE_SYSCALLS 1717 bool "Enable madvise/fadvise syscalls" if EXPERT 1718 default y 1719 help 1720 This option enables the madvise and fadvise syscalls, used by 1721 applications to advise the kernel about their future memory or file 1722 usage, improving performance. If building an embedded system where no 1723 applications use these syscalls, you can disable this option to save 1724 space. 1725 1726config MEMBARRIER 1727 bool "Enable membarrier() system call" if EXPERT 1728 default y 1729 help 1730 Enable the membarrier() system call that allows issuing memory 1731 barriers across all running threads, which can be used to distribute 1732 the cost of user-space memory barriers asymmetrically by transforming 1733 pairs of memory barriers into pairs consisting of membarrier() and a 1734 compiler barrier. 1735 1736 If unsure, say Y. 1737 1738config KCMP 1739 bool "Enable kcmp() system call" if EXPERT 1740 help 1741 Enable the kernel resource comparison system call. It provides 1742 user-space with the ability to compare two processes to see if they 1743 share a common resource, such as a file descriptor or even virtual 1744 memory space. 1745 1746 If unsure, say N. 1747 1748config RSEQ 1749 bool "Enable rseq() system call" if EXPERT 1750 default y 1751 depends on HAVE_RSEQ 1752 select MEMBARRIER 1753 help 1754 Enable the restartable sequences system call. It provides a 1755 user-space cache for the current CPU number value, which 1756 speeds up getting the current CPU number from user-space, 1757 as well as an ABI to speed up user-space operations on 1758 per-CPU data. 1759 1760 If unsure, say Y. 1761 1762config DEBUG_RSEQ 1763 default n 1764 bool "Enable debugging of rseq() system call" if EXPERT 1765 depends on RSEQ && DEBUG_KERNEL 1766 help 1767 Enable extra debugging checks for the rseq system call. 1768 1769 If unsure, say N. 1770 1771config CACHESTAT_SYSCALL 1772 bool "Enable cachestat() system call" if EXPERT 1773 default y 1774 help 1775 Enable the cachestat system call, which queries the page cache 1776 statistics of a file (number of cached pages, dirty pages, 1777 pages marked for writeback, (recently) evicted pages). 1778 1779 If unsure say Y here. 1780 1781config PC104 1782 bool "PC/104 support" if EXPERT 1783 help 1784 Expose PC/104 form factor device drivers and options available for 1785 selection and configuration. Enable this option if your target 1786 machine has a PC/104 bus. 1787 1788config KALLSYMS 1789 bool "Load all symbols for debugging/ksymoops" if EXPERT 1790 default y 1791 help 1792 Say Y here to let the kernel print out symbolic crash information and 1793 symbolic stack backtraces. This increases the size of the kernel 1794 somewhat, as all symbols have to be loaded into the kernel image. 1795 1796config KALLSYMS_SELFTEST 1797 bool "Test the basic functions and performance of kallsyms" 1798 depends on KALLSYMS 1799 default n 1800 help 1801 Test the basic functions and performance of some interfaces, such as 1802 kallsyms_lookup_name. It also calculates the compression rate of the 1803 kallsyms compression algorithm for the current symbol set. 1804 1805 Start self-test automatically after system startup. Suggest executing 1806 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1807 displayed in the last line, indicating that the test is complete. 1808 1809config KALLSYMS_ALL 1810 bool "Include all symbols in kallsyms" 1811 depends on DEBUG_KERNEL && KALLSYMS 1812 help 1813 Normally kallsyms only contains the symbols of functions for nicer 1814 OOPS messages and backtraces (i.e., symbols from the text and inittext 1815 sections). This is sufficient for most cases. And only if you want to 1816 enable kernel live patching, or other less common use cases (e.g., 1817 when a debugger is used) all symbols are required (i.e., names of 1818 variables from the data sections, etc). 1819 1820 This option makes sure that all symbols are loaded into the kernel 1821 image (i.e., symbols from all sections) in cost of increased kernel 1822 size (depending on the kernel configuration, it may be 300KiB or 1823 something like this). 1824 1825 Say N unless you really need all symbols, or kernel live patching. 1826 1827config KALLSYMS_ABSOLUTE_PERCPU 1828 bool 1829 depends on KALLSYMS 1830 default X86_64 && SMP 1831 1832# end of the "standard kernel features (expert users)" menu 1833 1834config ARCH_HAS_MEMBARRIER_CALLBACKS 1835 bool 1836 1837config ARCH_HAS_MEMBARRIER_SYNC_CORE 1838 bool 1839 1840config HAVE_PERF_EVENTS 1841 bool 1842 help 1843 See tools/perf/design.txt for details. 1844 1845config GUEST_PERF_EVENTS 1846 bool 1847 depends on HAVE_PERF_EVENTS 1848 1849config PERF_USE_VMALLOC 1850 bool 1851 help 1852 See tools/perf/design.txt for details 1853 1854menu "Kernel Performance Events And Counters" 1855 1856config PERF_EVENTS 1857 bool "Kernel performance events and counters" 1858 default y if PROFILING 1859 depends on HAVE_PERF_EVENTS 1860 select IRQ_WORK 1861 help 1862 Enable kernel support for various performance events provided 1863 by software and hardware. 1864 1865 Software events are supported either built-in or via the 1866 use of generic tracepoints. 1867 1868 Most modern CPUs support performance events via performance 1869 counter registers. These registers count the number of certain 1870 types of hw events: such as instructions executed, cachemisses 1871 suffered, or branches mis-predicted - without slowing down the 1872 kernel or applications. These registers can also trigger interrupts 1873 when a threshold number of events have passed - and can thus be 1874 used to profile the code that runs on that CPU. 1875 1876 The Linux Performance Event subsystem provides an abstraction of 1877 these software and hardware event capabilities, available via a 1878 system call and used by the "perf" utility in tools/perf/. It 1879 provides per task and per CPU counters, and it provides event 1880 capabilities on top of those. 1881 1882 Say Y if unsure. 1883 1884config DEBUG_PERF_USE_VMALLOC 1885 default n 1886 bool "Debug: use vmalloc to back perf mmap() buffers" 1887 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1888 select PERF_USE_VMALLOC 1889 help 1890 Use vmalloc memory to back perf mmap() buffers. 1891 1892 Mostly useful for debugging the vmalloc code on platforms 1893 that don't require it. 1894 1895 Say N if unsure. 1896 1897endmenu 1898 1899config SYSTEM_DATA_VERIFICATION 1900 def_bool n 1901 select SYSTEM_TRUSTED_KEYRING 1902 select KEYS 1903 select CRYPTO 1904 select CRYPTO_RSA 1905 select ASYMMETRIC_KEY_TYPE 1906 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1907 select ASN1 1908 select OID_REGISTRY 1909 select X509_CERTIFICATE_PARSER 1910 select PKCS7_MESSAGE_PARSER 1911 help 1912 Provide PKCS#7 message verification using the contents of the system 1913 trusted keyring to provide public keys. This then can be used for 1914 module verification, kexec image verification and firmware blob 1915 verification. 1916 1917config PROFILING 1918 bool "Profiling support" 1919 help 1920 Say Y here to enable the extended profiling support mechanisms used 1921 by profilers. 1922 1923config RUST 1924 bool "Rust support" 1925 depends on HAVE_RUST 1926 depends on RUST_IS_AVAILABLE 1927 depends on !CFI_CLANG 1928 depends on !MODVERSIONS 1929 depends on !GCC_PLUGINS 1930 depends on !RANDSTRUCT 1931 depends on !SHADOW_CALL_STACK 1932 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1933 help 1934 Enables Rust support in the kernel. 1935 1936 This allows other Rust-related options, like drivers written in Rust, 1937 to be selected. 1938 1939 It is also required to be able to load external kernel modules 1940 written in Rust. 1941 1942 See Documentation/rust/ for more information. 1943 1944 If unsure, say N. 1945 1946config RUSTC_VERSION_TEXT 1947 string 1948 depends on RUST 1949 default "$(shell,$(RUSTC) --version 2>/dev/null)" 1950 1951config BINDGEN_VERSION_TEXT 1952 string 1953 depends on RUST 1954 # The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0 1955 # (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when 1956 # the minimum version is upgraded past that (0.69.1 already fixed the issue). 1957 default "$(shell,$(BINDGEN) --version workaround-for-0.69.0 2>/dev/null)" 1958 1959# 1960# Place an empty function call at each tracepoint site. Can be 1961# dynamically changed for a probe function. 1962# 1963config TRACEPOINTS 1964 bool 1965 1966source "kernel/Kconfig.kexec" 1967 1968endmenu # General setup 1969 1970source "arch/Kconfig" 1971 1972config RT_MUTEXES 1973 bool 1974 default y if PREEMPT_RT 1975 1976config MODULE_SIG_FORMAT 1977 def_bool n 1978 select SYSTEM_DATA_VERIFICATION 1979 1980source "kernel/module/Kconfig" 1981 1982config INIT_ALL_POSSIBLE 1983 bool 1984 help 1985 Back when each arch used to define their own cpu_online_mask and 1986 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1987 with all 1s, and others with all 0s. When they were centralised, 1988 it was better to provide this option than to break all the archs 1989 and have several arch maintainers pursuing me down dark alleys. 1990 1991source "block/Kconfig" 1992 1993config PREEMPT_NOTIFIERS 1994 bool 1995 1996config PADATA 1997 depends on SMP 1998 bool 1999 2000config ASN1 2001 tristate 2002 help 2003 Build a simple ASN.1 grammar compiler that produces a bytecode output 2004 that can be interpreted by the ASN.1 stream decoder and used to 2005 inform it as to what tags are to be expected in a stream and what 2006 functions to call on what tags. 2007 2008source "kernel/Kconfig.locks" 2009 2010config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2011 bool 2012 2013config ARCH_HAS_PREPARE_SYNC_CORE_CMD 2014 bool 2015 2016config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2017 bool 2018 2019# It may be useful for an architecture to override the definitions of the 2020# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2021# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2022# different calling convention for syscalls. They can also override the 2023# macros for not-implemented syscalls in kernel/sys_ni.c and 2024# kernel/time/posix-stubs.c. All these overrides need to be available in 2025# <asm/syscall_wrapper.h>. 2026config ARCH_HAS_SYSCALL_WRAPPER 2027 def_bool n 2028